Glass-enclosed atrium or greenhouse structures are being used with greater frequency in restaurants and commercial buildings as well as homes. While these structures have many aesthetic advantages and are pleasing architecturally, in direct sunlight they become practically uninhabitable with severe discomfort on the part of the occupants. Consequently, it is necessary to provide some sort of a shading device which may readily be raised or lowered. Because these structures typically involve a vertical wall of glass which, at its topmost portion is curved to a 45.degree. angle with the upper portion extending at such an angle until it joins the conventional portion of the structure, ordinary shades or blinds will not function because they would hang in an unattractive, ineffective fashion because of the overhanging curved portion of the atrium.
Therefore, it is necessary to provide tracks on which the shades can be supported and, as a consequence, these atriums or greenhouses are usually constructed in sections with tracks spaced two or three feet apart. The shades are thus supported on transversely extending rods that ride in said tracks and the shades are usually permitted to descend by gravity and may be raised by hand or by means of a motorized device. In any case, the shades occasionally will stick in one or the other tracks so that the shades will be askew and cause an unattractive appearance. This can occur either when the shade is raised or when it is lowered.
Power driven devices are available to raise or lower the shades, but these are relatively expensive and in many applications, especially where the atrium or greenhouse is small, it is desirable to have the shades operated manually. The only device of the prior art with which applicant is familiar is U.S. Pat. No. 2,229,898, Pastva, which is an awkward device to use for raising or lowering blinds in these circumstances and involves separate pulls which would not function in the overhanging atrium or greenhouse configuration. Furthermore, this system does not permit self-leveling of the blinds in case they become stuck while being raised or lowered.